Braiding machines have long been known in the art for braiding-multiple filaments of materials, e.g., synthetics, plastics or metals, such as copper or stainless steel wire, at reasonably high production rates. One type of braiding machine, which is commonly referred to as an internal cam rotary braider, has been known to the art for many years. One of the best-known rotary (a.k.a. “circular”) braiders is the Wardwell Rapid Braider (hereinafter the “Rapid Braider” or “Wardwell rotary braiding machine”), made and sold by Wardwell Braiding Machine Company of Central Falls, R.I., U.S.A. (hereinafter “Wardwell”). Wardwell is the Assignee of the current application.
Wardwell rotary braiding machines have been available in various sizes, depending on the number of filaments required in the final braided output, and have been in use for many decades since the first designs were introduced about the turn of the century. Their reliability and relatively high speed of operation have been well recognized. Such machines have been used satisfactorily over the years, normally requiring only the replacement of parts. Hence, their structure and operation have essentially remained unchanged since their original design.
Simon W. Wardwell co-invented the Rapid Braider machine at the Wardwell Braiding Machine Company. U.S. Pat. No. 1,423,587 entitled “YARN RETRIEVER FOR BRAIDING OR OTHER MACHINES” issued on Jul. 25, 1922. It disclosed and claimed the Rapid Braider.
An improved rotary braider, called the “Speed Master” (not shown), was later invented at the Wardwell Braiding Machine Company. The Speed Master changed the angle of the braid feed.
Both the Rapid Braider and the Speed Master machines represent a broader class of rotary braiding machines for braiding filaments of fiber, thread or other spoolable medium about a common central axis. They are also known as deflector type rotary braiding machines.
As shown in FIGS. 1-3 of U.S. Pat. No. 1,423,587 (reproduced in the current application as FIGS. 1, 7 and 2 respectively), the Rapid Braider machine comprises: a radially more inward tray of bobbins, i.e., an upper array of bobbins; and a radially more outward array of similar bobbins, i.e., a lower array of bobbins). The upper and lower arrays of bobbins rotate in opposite directions about a common center axis. As each array rotates, its bobbins supply filament to, and wind the filament around, a mandrel at the axis. Filament deflectors and guides associated with each lower bobbin direct the filament therefrom alternately below and above the upper bobbins as the bobbin arrays rotate. This process produces the braid. The alternating deflection of the lower bobbin filament above and below the upper bobbins can be set up to occur with any number of upper bobbins to obtain the desired braid pattern.
FIG. 3 of U.S. Pat. No. 1,423,587 shows sample deflector guides. These guides have both an upper and lower contour for deflecting the filament. If the filament impacts on the top surface, it gets deflected over the upper bobbin. If the filament impacts the lower surface; it remains below the upper bobbin. In this fashion, the weave of the braid is formed as the bobbin arrays rotate in opposite directions. That same drawing figure also presents the lower bobbin tension control arm which is used to take up filament slack and minimize tension as the filament is being deflected. This lever acts as an idler arm and a tension control device. This same lever arm, when deflected over a large angle, releases a ratchet mechanism on the lower bobbin which allows the bobbin to turn and feed filament. Typically this release occurs near the height of the filament deflection process.
New engineering analyses and tests (by the current Applicants) of failure mechanisms on both the Rapid Braider and Speed Master machines have shown that most failures, or filament breakage during braiding, are a result of tension spikes in the filament set up by impulsive forces generated during the spool feed process on the machines' lower bobbins. These tension spikes result from: the rapid rotational acceleration and deceleration required of the lower bobbin as a result of the feed process, the lever arm tension control device, the actuation of the bobbin ratchet mechanism and the shape of the filament deflector surface required for the braiding operation. Such failure limits the operating speed of rotary braiding machines, and/or the minimum size of filament that can be braided effectively, and/or the ability to maintain the quality of the braid.
Accordingly, it is a general object of the present invention to provide a new powered bobbin feed which improves the braiding process of deflector type rotary braiding machines, such as the Rapid Braider or Speed Master.
It is another general object to provide a new Powered Lower Bobbin Feed for deflector type rotary braiding machines, which reduces the unwanted stresses placed on a filament of material being handled thereby, reducing breakage in the braiding process.
It is yet another general object to provide a new Powered Lower Bobbin Feed for deflector type rotary braiding machines, which can increase the working speed of rotary braiding machines.
It is yet another general object to provide a new Powered Lower Bobbin Feed for deflector type rotary braiding machines, which can improve the uniformity of braided filaments generated by such machines at a given speed.
It is a more specific object, commensurate with the above listed objects, to eliminate tension spikes on a filament of material being handled by a rotary braiding machine by replacing the conventionally used lower carrier members of such machines with a new Powered Lower Bobbin Feed.